The present invention is related to optical networks and, more particularly to, safety and protection measures and procedures in such networks.
When a fault occurs in the transmission of signals from a source node to a destination node, such as a break in an optical fiber, the protection measures of the optical network cause the rerouting of the signals to ensure the delivery of optical signals to their destination. There are different ways to protect optical networks against faults. One protection mechanism used in point-to-point links is the 1+1 mechanism in which the source node sends duplicate signals on two separate fibers to the destination node. The destination node receives the optical signals over one fiber, called the working fiber, and switches to the other fiber, called the protection fiber, in case a fault occurs with the first fiber to continue receiving the signals. Another protection mechanism is the 1:1 mechanism (a special case of 1:N protection) in which the source node sends optical signals over the working fiber to the destination node. In case of a fault in the transmission, the source node then switches the transmission of optical signals to the protection fiber. (In the 1:N mechanism there is one protection fiber for N working fibers.)
The sources of these signals for optical networks are lasers. While the lasers used in optical networks have relatively low power compared to, for example, industrial lasers, they are powerful enough to damage the human eye. Therefore safety measures are required for optical networks to avoid injury to human operators and service personnel. A typical safety protocol is OFC (Open Fiber Control) which has measures to detect cuts in optical fiber links, turn off the lasers connected to the link, and then allow low-level laser pulses intermittently on the cut fiber link for the link to be brought back into full operation upon the repair of the cut fiber.
In optical networks modularization of components is highly desirable because of ease of maintenance and repair and these protection and safety measures have been installed in separate modules in accordance with the function of the modules. However, optical networks still have problems in implementing protection and safety measures. The present invention is directed toward the optimum and practical realization of protecting the integrity of network signal delivery and ensuring the safety of human operators.